The present invention relates in general to flexible, annular cutting mats, and in particular to cutting mats having nonlinear edges.
Rotary die cutting machines are utilized to perform cutting operations in numerous industries. For example, the corrugated industry utilizes rotary die cutting machines to cut and score corrugated paperboard materials for constructing packaging products such as boxes and shipping containers. Basically, these machines pass a continuously moving workpiece through the nip of a cutting roller and a rotary anvil. The cutting roller includes cutting blades that project from the surface thereof, to provide the desired cutting actions to the workpiece. The rotary anvil includes several cutting mats aligned axially about the anvil surface to support the workpiece at the point where the work material is scored by the cutting blades of the cutting roller. The cutting mats serve as a backstop allowing the cutting blades to be urged against the workpiece being cut without damaging the cutting blades themselves.
During use, the cutting blades on the cutting roller penetrate the cutting mats. This leads to eventual fatigue and wear of the cutting mats, requiring that the cutting mats be periodically replaced. However, it is unlikely that all of the cutting mats will wear evenly. For example, at times, rotary die cutting machines operate on a workpiece such that the full width of the rotary die cutting machine is not used. Under this circumstance, certain cutting mats experience most of the wear. Further, as the cutting mats wear, the quality of the cutting operation deteriorates.
Rotating the relative positions of the cutting mats on the rotary anvil such that the cutting mats wear more evenly may prolong the serviceable life of cutting mats. However, repositioning the cutting mats causes downtime because the rotary die cutting machine cannot be in operation when changing or adjusting the cutting mats. Because of downtime, the industry tendency is to prolong the time between cutting mat changeovers. This can lead to a greater possibility of poor quality cuts.
When multiple cutting mats are installed on a rotary anvil, a number of seams are created. For example, there is a circumferential seam between each adjacent cutting mat. Also, there is an axial seam between the opposite ends of each cutting mat. Modern rotary die cutting machines allow a great degree of flexibility in positioning the cutting blades on the cutting roller. The orientation of the cutting blades, especially when positioned axially or orthogonal to the axial dimension, can at times, strike the cutting mats along one or more seams. As a consequence, a cutting blade may slip through a seam possibly damaging the cutting blade. For example, if a cutting blade is positioned along an axial dimension of the cutting roller, the cutting blade can strike the rotary anvil along the axial seam defined between opposite ends of one or more cutting mats. Likewise, if a cutting blade is positioned orthogonal to the axial direction, the cuffing blade can strike a circumferential seam between adjacent cutting mats.
A die cutting machine must exert increased pressure to achieve a satisfactory cut when the cutting blades of the cutting roller slip between the seams defined by or between cutting mats. This increased pressure may shorten the life potential of the cutting mat, may lead to cutting blade damage, and may require more frequent maintenance of the cutting roller.
The present invention overcomes the disadvantages of previously known cutting mats by providing cutting mats that include at least one edge having a nonlinear shape. By nonlinear shape, it is meant that at least one edge of the cutting mat does not follow a single, straight path across the entire length of that edge. For example, a cutting mat according to one embodiment of the present invention comprises nonlinear circumferential edges. Cutting mats are aligned on a rotary anvil such that adjacent circumferential edges abut in mating relationship. The nonlinear circumferential edges of the cutting mats are configured such that when two cutting mats are properly installed on a rotary anvil, and are in abutting relationship, a cutting blade from a cutting roller cannot penetrate between the seam defined by two adjacent cutting mats.
A cutting mat according to another embodiment of the present invention comprises opposing nonlinear axial edges. By nonlinear axial edges, it is meant that the axial edges of the cutting mat do not follow a single, straight path across their entire length. The cutting mat is installed on a rotary anvil such that opposite, nonlinear edges abut in mating relationship. The nonlinear axial edges of each cutting mat are configured such that when the cutting mat is properly installed on a rotary anvil, a cutting blade from a cutting roller cannot penetrate between the seam defined by the axial edges.
According to yet another embodiment of the present invention, a cutting mat comprises nonlinear axial edges as well as nonlinear circumferential edges. The nonlinear circumferential edges of the cutting mats are configured such that when two cutting mats are properly installed on a rotary anvil, and are in abutting relationship, a cutting blade or other scoring element from a cutting roller cannot penetrate between the seam defined by two adjacent cutting mats. Likewise, the nonlinear axial edges of each cutting mat are configured such that when each cutting mat is properly installed on a rotary anvil such that the opposite nonlinear axial edges are in abutting relationship, a cutting blade or other scoring element from a cutting roller cannot penetrate between a seam defined by the axial edges of the cutting mat.